The invention relates to a front-hood arrangement wherein a front hood of a vehicle is coupled to the frame of the vehicle via a hinge, which front hood furthermore can be closed by means of at least one hood lock.
By now, numerous safety devices, such as airbags and the like, for passengers in automobiles are known from practical applications. By contrast, protective measures for pedestrians who are hit by the front end of a passenger automobile have to date scarcely been proposed or implemented in practice. Accidents involving pedestrians which take place at speeds of up to 60 km/h have proven particularly problematical, since, if the pedestrian is hit head-on, his head often strikes the engine hood of the passenger automobile, and the pedestrian dies from his injuries. The seriousness of the injury results from the fact that although the front or engine hood, which is usually formed from thin metal sheet, would tend to bend, it then strikes parts which are arranged beneath the engine hood and in practice cannot be deformed or can only be deformed with difficulty, such as the engine block, the suspension-leg carrier, the air filter, the valve cover or the frame side and cross members of the vehicle. It would be desirable if the consequences of an impact in particular of the head of a pedestrian could be made less severe. By contrast, at speeds of over 60 km/h, the pedestrian, after he has been hit, is thrown over the vehicle.
DE-C-29 22 893 proposes that the engine hood and the wing, in the region of the joint formed between these two parts, be supported, by means of energy-absorbing U-sections which run along the two parts, on body components, and in the event of a collision these U-sections convert the impact into deformation energy. A first drawback of this arrangement is that considerable forces have to act on the sections in order to bend them. Moreover, these otherwise useless U-sections are expensive to procure and difficult to fit.
DE-A-27 37 876 describes an impact protection device which uses a prestressed pivot flap to displace a mesh-like absorption element out of an at-rest position, in which the mesh rests substantially on the front hood, into an absorbing position, which runs substantially in front of the windshield of the automobile. This device is used more to protect the windshield than the pedestrian from an excessively hard impact on the front hood. Moreover, any contact with the sensor which triggers the pivoting movement and is integrated in the front bumper can cause the mesh to be triggered, with the result that a whole range of situations arise in which the mesh completely blinds the driver.
DE-A-28 41 315 describes a safety device in which, in reaction to a signal from a sensor arranged at the front of a vehicle, to detect a collision with a pedestrian, the front hood is displaced out of an at-rest position into an impact position, which is raised with respect to the at-rest position, by a piston-cylinder unit, the displacement being effected by an energy store. During the raising operation, the front hood is pivoted about a horizontal pivot pin which is arranged at the front of the vehicle.
DE-A-197 10 417 describes an arrangement for lifting the front hood in which pivoting about a horizontal pivot pin arranged at the front of the vehicle is triggered by the same pneumatic spring which also assists with the raising of the front hood which is coupled to the other end.
DE-A-197 21 565 describes a safety device on motor vehicles for raising the front hood in which the raising of the front hood takes place in a speed-dependent manner by means of a mechanism which is integral with the hood lock. For this purpose, either the unlocking of the lock which is acted on by a compression spring, which for safety reasons is normally triggered from the driver""s compartment, is triggered by a sensor which is triggered by an impact, or alternatively, particularly at relatively high speeds, a piston-cylinder unit which is integrated in the catch bolt of the hood lock is expanded by a propelling charge. A first drawback of this arrangement is that the force required to close the front hood must not exceed a defined threshold, in order to allow the driver to close the front hood with ease. Since the forces which strike in the event of an accident involving a person are considerable, the front hood is pressed down rapidly, and the known injuries occur, in particular in the region of the head. Providing a propelling charge in order to expand a piston-cylinder unit also causes problems, since the service life of this charge, in particular in a relatively unprotected arrangement, is limited, and the charge is difficult to exchange. Moreover, there is a risk of the compression spring and the piston-cylinder unit being triggered simultaneously, with the result that the opening of the front bonnet would become so great that the airstream would bring the hood into contact with the windshield, thus preventing the driver from being able to see.
DE-A-27 11 338 describes a device for damping the impact of a pedestrian, in which an airbag is arranged in the region of the cowl, the filling of which airbag is triggered by a sensor signal. In this case, the airbag may be arranged in such a way that, at the same time, it raises a part of the front hood; to do this it overcomes a spring force which preloads two links, which are connected to one another via a rotation point and one of which is arranged rotatably on the front hood and the other of which is arranged rotatably on a fixed part of the motor vehicle, into an angled position. Furthermore, it is proposed to arrange resilient profiled bodies in strip form in the manner of a seal between hood and side parts, in order in this way to provide further protection in the event of an impact.
DE-A-27 11 339 describes a front hood which is coupled at the front side and in which the coupling is designed to be resilient, in such a manner that it allows a horizontal displacement of the front hood through the impact of a pedestrian, the front hood which is displaced toward the rear being connected at the rear side to one end of a rigid locking element, the other end of which, in the event of displacement of the front hood, is displaced upward and toward the rear in a guide curve in such a manner that the front hood executes an upward movement. This lifting only takes place if horizontal displacement of the front hood has actually occurred, which is not always the case, for example, in the event of impacts of children.
EP-A-0 509 690 describes a front hood, which at its front side is coupled to the vehicle structure in such a manner that, as a result of an impact, the front hood is displaced toward the rear, the closure or pivot means arranged at the rear side, as a result of a movement of the front hood toward the rear, triggering an upward pivoting movement of the front hood, so that the deformation travel of the hood is increased in the event of the impact of a pedestrian. The pivoting movement is guided, for example, by a four joint hinge, which is otherwise used to pivot the front hood when it is desired to release access to the engine and other parts. In this case too, the front hood is only lifted in the event of a very substantial displacement of the front hood, while a weak impact does not displace the front hood toward the rear and therefore upward.
DE-C-30 47 969 describes a front-hood arrangement in which deformation members which, in the event of the impact of a pedestrian on the front hood, resiliently damp the impact, are formed between the front hood and the body outside the hinges.
DE-A-197 12 961 describes the arrangement of a front hood on a vehicle in which a hinge is arranged on a hinge mount, which hinge, in the event of a collision with a pedestrian, is pivoted upward in order to raise the front hood. A problem of this arrangement is that the hood lock for the front hood defines a pivot axis which does not allow optional displacement of the hinge mount, and consequently the hinge mount described is, for example, blocked.
Overall, as yet no solution has been proposed which proposes an inexpensive arrangement, which can be readily restored after use and which is so well developed that it could be used in mass-produced vehicles.
It is the object of the invention to propose a front-hood arrangement that supplies pedestrian protection that can be achieved inexpensively and on an industrial scale.
This object is achieved for the front-hood arrangement described at the beginning, according to the invention, in that the hinge, in the event of an impact of a pedestrian, undergoes a plastic deformation.
The front-hood arrangement according to the invention, in the event of a collision with a pedestrian, enables the front hood which is arranged to a corresponding degree above the dangerous parts, such as engine block and the like, to be arranged relatively close to these parts, so that the styling of the vehicle does not need to suffer from the higher hood. In a similar manner as that used for desired breaking points, soft elements are inserted in the hinges, allowing controlled deformation in terms of position and orientation as a result of the impact of a body on the front hood, with the result that, at the same time, it is ensured that, firstly, the relative movement about the hood lock which defines a pivot axis of the front hood becomes possible and, secondly, the impact energy effects a defined deformation energy during the plastic deformation of the hinge elements.
According to a preferred refinement of the invention, it is provided that a force which acts substantially normally with respect to the front hood triggers the deformation of the hinge by overcoming low oppositely directed forces, while in the event of an axial compressive load on the vehicle, which is to be expected as the principle direction of load in the event of a head-on collision with another vehicle, the hinge elements which bear the front hood remain substantially unchanged or are scarcely plastically deformed, so that the crash behavior of the vehicle overall is not impaired by the measure used to protect pedestrian who have been struck.
Expediently, the front hood is not only raised at its rear region by the hinge units designed according to the invention with respect to a final position after collision with a pedestrian, but also the hood lock is arranged in a raised position which allows yielding in response to the impact of a human body, the displacement travel of the hood lock being taken into account when designing the desired bending points of the hinge elements.
Designing the hinge elements as plastically deformable connections between front hood and, for example, the frame side member of the motor vehicle ensures that, after the impact of the human body there is no recoil from the prestress of the bent hinge elements which throws the pedestrian back onto the roadway, but rather by far the greatest part of the impact energy is converted into deformation energy and is thus reduced for the pedestrian. This considerable transformation of energy alleviates the impact in particular of a head of a pedestrian in such a manner that it may be life-saving, yet only minor investment costs are required for this measure.
It is possible to couple the plastically deformable hinge elements to the frame side member of the motor vehicle by means of extendable lifting members or the like which enable the front hood, when an impact is detected, for example by a sensor arranged in the front strip of the vehicle or by other suitable means, to be extended upward, the front hood then, by means of a plastic deformation of the upwardly extended hinge elements, being deformed substantially back into its starting position, the specific deformation travel depending on the vehicle speed and the hardness and position of the impact. It should be noted that, when using such lifting members, the time which elapses before the lifting members are extended should if possible be less than {fraction (1/10)} second, so that the maximum travel has already been covered when the pedestrian or his head strikes the hood. The extension of the lifting members can be triggered both by pneumatic and hydraulic piston-cylinder units with respect to the units and pyrotechnically or mechanically.
If possible, the deformation travel provided as a result of the front hood being raised above the supporting and solid parts of the engine compartment should be 120 mm and at least 70 mm, in order to ensure a sufficiently long travel for the transformation of the impact energy. In this context, it should be taken into account that the front hood, which is generally produced from sheet metal, in the event of a central impact can itself undergo considerable deformation, and in the event of an eccentric impact the extent of utilization of one of the two front-hood hinges may be greater than that of the other front-hood hinge. However, it is possible, when providing relatively rigid front hoods, for example those made from glass-fiber-reinforced plastics or which have a reinforcing matrix of glass fibers, which reduces the deformation of the front hood itself, which initially increases the danger of the impact, to improve by the inventive transmission of the impact energy to the hinges, so that a significantly higher energy can be absorbed in the hinges and therefore, as a result, lower overall heights can be achieved. This plays a role in particular in the event of a collision with children which takes place in the front region of the front hood and in which the lever arm for the transmission of the forces is different from that involved in a collision with an adult.
A significant advantage of the hinges being designed as plastically deformable parts consists in the fact that these parts can be replaced with little difficulty, for example if they have been inadvertently triggered or after a collision with a pedestrian. Unlike with pyrotechnic charges and the like, a plastic change in the hinge parts remains possible even after the vehicle has been used for a prolonged period. Finally, it should be noted that, in the arrangement according to the invention, the front hood can generally be opened even after the deformation caused by an impact has ended, once the hood lock has been unlocked, so that the state of the engine compartment can be checked quickly following an impact.
It is possible to design any configurations of hinges which are known per se, through execution of plastic deformation, in such a manner that the front hood yields under the impact of a pedestrian and is pivoted out of a raised, ready-to-drive starting position into a lowered position. If the hinge is designed as a single joint, it is expedient for the region which is mounted on the body to be plastically deformable. If the hinge is desired as a multiple-joint hinge, e.g. as a four-joint hinge, it is also possible for one link or expediently a plurality of links or all the links to be plastically deformable.
The plastic deformation is not necessarily restricted to the material of the hinges themselves. Rather, it is possible for energy stores which are designed in the manner of a desired breaking point also to be integrated with the hinge, with the result that the plastic deformation converts energy through the deformation of these energy stores. In particular, parts which can be elongated or sheared off are advantageously used for this purpose.
Further advantages and features of the invention will emerge from the following description and from the dependent claims.